Evidence for nitric oxide-generator cells in the brain.

L Ma
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Abstract

Nitric oxide (NO) is a free radical that has been recently recognized as a neuronal messenger molecule. In order to understand the way in which NO functions in the central nervous system (CNS), it is important to identify the NO-generator and NO-target cells in the brain. I measured firstly the distribution of NO synthase in the brain, which catalyzes L-arginine to form NO, by the measurement of citrulline formation that is also synthesized from L-arginine together with NO in equal molar bass. In the brain of adult rat, the most potent activity of NOS was apparent in the cerebellum, next in the olfactory bulb and medium in the cerebrum. Further, in the presence of NADPH and Ca2+, NOS activity was detected in the neuron cultures derived from the cerebrum of fetal rat. Astrocytes, one type of glia, prepared also from the cerebrum of fetal rat, appeared to have a small but significant NOS activity. As astrocytes possess a high amount of cytosolic guanylate cyclase that is known to be activated by NO, the changes in the intracellular cGMP levels in the astrocytes were measured as another index of NO formation. The treatment of astrocytes with NOS inhibitor caused the suppression of the intracellular cGMP levels. These results indicate that NO is definitely produced by astrocytes. In addition, in the blood vessel system of the brain, although NOS has been thought to be localized in the endothelial cells of only larger vessels, NOS activity was also observed in the microvessel endothelial cells of the cerebrum of both adult and fetal pig. These data suggest that neuronal cells may be the major site of NO generation in the brain, and that the NOS is a constitutive type. The data also suggest that astrocytes can also express constitutive NOS, although the potency is not so large. Microvessel endothelial cells of the brain are also one of the sources of NO. The NO produced by these cells increases the cGMP levels in the astrocytes and may affect some physiological and/or pathophysiological events in the brain.

大脑中有一氧化氮生成细胞的证据。
一氧化氮(NO)是一种自由基,近年来被认为是一种神经信使分子。为了了解一氧化氮在中枢神经系统(CNS)中的作用,识别大脑中的一氧化氮产生细胞和一氧化氮靶细胞是很重要的。我首先测量了大脑中催化l -精氨酸生成NO的NO合成酶的分布,通过测量同样由l -精氨酸与NO在等摩尔低音中合成的瓜氨酸生成量。在成年大鼠的大脑中,NOS的活性以小脑最强,其次是嗅球,中脑为中脑。此外,在NADPH和Ca2+存在的情况下,在胎鼠大脑的神经元培养物中检测到NOS活性。星形胶质细胞是一种同样从胎鼠大脑中制备的胶质细胞,其NOS活性虽小但显著。由于星形胶质细胞具有大量的胞浆鸟苷酸环化酶,已知该酶可被NO激活,因此测量星形胶质细胞内cGMP水平的变化作为NO形成的另一个指标。NOS抑制剂处理星形胶质细胞可抑制细胞内cGMP水平。这些结果表明NO一定是由星形胶质细胞产生的。此外,在脑血管系统中,尽管NOS被认为只局限于大血管内皮细胞,但在成年猪和胎儿猪的大脑微血管内皮细胞中也观察到NOS活性。这些数据表明,神经元细胞可能是脑内NO生成的主要部位,而NOS是一种组成型。星形胶质细胞也能表达组成型NOS,但其表达能力没有那么大。脑微血管内皮细胞也是一氧化氮的来源之一。这些细胞产生的NO增加了星形胶质细胞中的cGMP水平,并可能影响大脑中的一些生理和/或病理生理事件。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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